Networked attached storage (NAS) and storage area networks (SANs) are two recent technologies that attempt to allow computers to access network-connected hard disk drives and other mass storage devices using block-level commands so that the networked storage appears to be accessed as if it were physically attached to the workstation. In a NAS, the storage device connects directly to the network medium and does not require an intermediate server to provide access to the storage. In a SAN, a separate network of storage devices forms storage space that is allocated to different workstations and this separate network is itself connected to the network medium, which connects the different workstations.
Conventional SANs do not perfectly solve all the mass storage needs for an enterprise. In particular, maintenance and provisioning of the storage space within the conventional SAN is difficult to accomplish and wasteful of the physical resources. To address these concerns, many recent developments in this field have involved virtualizing the storage space so that there is little, or no, correlation between the physical disk drive devices where the data actually resides and the logical disk drive devices which are the targets for a workstation's data access request. One such currently produced product that is known in the industry and provides a substantially virtualized view of the storage space within a SAN is the MAGNITUDE® SAN manufactured by Xiotech Corporation of Eden Prairie, Minn.
The MAGNITUDE® SAN aggregates physical drives into a centralized “virtualized” storage pool and has the ability to stripe across and utilize all available space in a centralized storage pool. From this pool, a user carves out storage into “virtualized disks” and assigns that storage to whichever workstation that needs it. Within the SAN, the workstations see the MAGNITUDE® SAN's virtual disks as Logical Unit Numbers (LUNs). Within MAGNITUDE® SAN, virtualization refers to different levels of logical constructs rather than to physical storage devices (e.g. SCSI hard disk drives).
The MAGNITUDE® SAN is responsible for presenting the available virtualized disks as addressable devices on the Fibre Channel fabric. As a result, remote servers and workstations need only generate a typical block-level command (e.g., SCSI-3 command) to access blocks on an available logical drive. The MAGNITUDE® SAN, however, receives this conventional protocol request and converts it into a virtual request packet (VRP) for internal processing. The MAGNITUDE® SAN internally unencapsulates, parses and processes a VRP message utilizing translation tables in order to eventually generate SCSI commands to access multiple SCSI devices.
The MAGNITUDE® SAN enforces access controls at the virtualized disk level. Individual virtualized disks can be assigned to a specific workstation to allow the workstation and its storage to be isolated from another workstation and its storage.
Within the MAGNITUDE® SAN system, for example, there is at least one controller having firmware, that when executed, performs the many levels of translations needed to permit receiving a request involving a virtualized drive and actually performing data accesses to multiple physical devices.
The firmware in the controllers occasionally requires upgrades to improve performance. However, the servers and workstations must be powered down during such firmware upgrades. Accordingly, being denied access during these firmware upgrades may inconvenience customers utilizing the SAN. There remains the need, therefore, for a method of upgrading firmware in a controller without inconveniencing the users of the system.